THE FAMILY ROTALIID.E 223 



deposits of the present day, where it often constitutes 

 the larger proportion of the material. It is widely 

 distributed in its geographical range both north and 

 south of the equator. Its geological occurrence 

 commences in the Chalk-marl, and it is found at many 

 horizons in Tertiary strata. (Plate 12, figs. L, /, /'.) 



GrENUs liotalia, Lamaeck. 



Test Eotaliform, shell-wal] very finely porous ; 

 with an exogenous deposit in the form either of 

 embossed septal lines or of granulation of the sutures 

 near the umbilicus. Aperture a neatly arched slit, 

 nearly median. Larger species have double septa 

 and a system of interseptal canals. Lower Cretaceous 

 to Uecent. 



Example. — -it. Holdanii, D'Orbigny sp. (Botalii/a), 

 'Ann. Sci. Nat.' vol. vii. 1826, p. 278, No. 5 ; ' Modele,' 

 No. 36. 



The shell of this species exhibits the extreme 

 type of the plano-convex BotaluF. B. Soldanii is 

 widely distributed in our modern seas, and occurs 

 most frequently at depths between 1,000 and 2,000 

 fathoms. The type-form first makes its appearance 

 in strata of Eocene age, whilst the variety nit id a has 

 been recorded from beds as old as the Gault. (Plate 

 12, figs. M, m.) 



Genus Calcariiui, D'Oebigxy. 

 Test Eotaliform, lenticular ; periphery furnished 

 with radiating (sometimes branching) spines ; supple- 

 mental skeleton and canal system very largely 

 developed. Chcdk to Becent. 



